A few random (and perhaps incoherent) thoughts on spotlighting hardware ...
The first thought that always comes to my mind when this discussion topic
comes up is "How powerful a spotlight is actually necessary to observe
wildlife at night?". Is a 100 Watt (100W) light any better than a 75W? - at
least in terms of what use a human eye can make of the output of either
unit.
I'm not too sure about the candlepower unit and what that means in the real
world, but spotlights are generally categorised by manufacturers in terms of
the power (in Watts) of the globe. Design of the reflector and/or globe
might vary the light output from otherwise similar globes rated at the same
wattage. One manufacturer of spotlights in Australia sells handheld units
with a number of different globes - 30W, 40W, 50W, 75W and 100W.
Up until now, I've always used an old 30W/*6V Watco spotlight, and found it
more than adequate for all forest and woodland spotlighting. It's a bit
under powered in grassland and other very open habitats, and the light is
relatively yellow compared to other systems I've seen in action alongside
it. I recently upgraded to a 75W/*12V system with a halogen globe, and have
been very impressed with its performance in the field so far. This is a
standard configuration from that manufacturer, otherwise I'd probably have
gone for a 40 or 50W. I compared it with a 100W system, and judged that
there was no measurable benefit from the extra 25W of power consumption, ie.
my eye was unable to see any further or better with a 100W vs. a 75W light.
The 75W light puts out a prodigious amount of very white looking light - so
I've also purchased a diffusing filter to scatter the light more when
working close up to animals. Jack Pettigrew did make the point that
although powerful spotlights might not cause permanent damage, temporary
blindless might be caused, and this may make the animal more prone to
predation. I tend to exercise the precautionary principle, and put as
little light on the animal as is necessary to identify or observe it. Most
lights put out less intense, scattered light as a halo around the
concentrated spot, and I find that it's easy to use the spot to find the
animal, then the duller halo to observe. I udge that I'm having the minimum
impact possible on the animal by doing it this way, and it is no less
effective for the purposes of survey/study, etc.
Battery life and size are important matters that people may sometimes
overlook. If you are intending to use the light only from the car (plugged
in to the cigarette lighter), then it really matters little how power hungry
the light is. If you are going on foot carrying the battery, then it makes
a big difference. With a 75W or 100W, 12V light, in order to be able to
spotlight continuously with just one battery for about 1-2 hours, you'll
need something like a 17A/h battery. These are big and heavy, and you need
to try one out to see if you can carry it over uneven ground for any length
of time. A much lighter 7A/h battery with 75 or 100W light would last about
20-30 minutes, but would be a great deal easier to carry. A 7A/h battery
with a 30W light would last maybe 1.45 hours, and would be quite effective
in most forest/woodland environments. Choosing a battery is at least as
important as choosing a light - the combination of the two makes a great
deal of difference in terms of how long you can be out there before needing
a fresh battery, or perhaps a pack animal to carry the thing!!
When I started spotlighting about 25 years ago, we carried standard 6V lead
acid motorcycle batteries in wooden boxes. These things leak whenever
they're tipped a bit off vertical, which led to lots of holes in clothing
etc. from the acid. Most people use sealed lead acid batteries these days,
and I'd recommend them very highly. They're relatively inexpensive, they
don't leak in use or while bumping around in the car, and are quite durable
if looked after nicely! They're available in both 6 and 12V formats, which
the old wet cells were not - hence me starting out with a 6V system. 12V
batteries can be charged from the car system with a relatively simple
intermediary device - 6V isn't as straight forward unless you have an old
Volkswagen!!
L.
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L A W R I E C O N O L E
2/37 Myrnong Crescent, Ascot Vale, Victoria 3032 AUSTRALIA.
Phone AH (03) 9370 3928; Mobile (0419) 588 993.
E-mail:
Senior Zoologist
Ecology Australia Pty Ltd
88 B Station Street, Fairfield, Victoria 3078 AUSTRALIA
Phone BH (03) 9489 4191
E-mail:
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